For example, as a device suitable for the transfer of heavy articles, a transfer device described in Japanese Examined Patent Application, Second Publication No. H03-78325, is proposed already. In the transfer device described in Japanese Examined Patent Application, Second Publication No. H03-78325, a carriage is movable on rails on a lifting table of a stacker crane, other rails capable of moving the carriage communicating with the rails of the lifting table and being provided in each storage portion of a warehouse, and a support for articles is provided on the carriage through lifting cylinders capable of lifting and lowering the articles. In addition, in the transfer device, a rack gear or a chain is fixed to the carriage along a side surface thereof, and pinions or sprocket wheels capable of being engaged with the rack gear or the chain and drive units thereof are provided in the lifting table at at least the front and back positions of the carriage.
In the transfer device, positioning pins to accurately position the lifting table with respect to the warehouse are provided in the lifting table at the front, back, left and right positions thereof so as to be capable of protruding and retracting in the direction toward the warehouse by cylinder units. The positioning pins are engaged with an upper surface or the like of the bottom of the storage portion in the warehouse, thereby performing the positioning of the lifting table. In Japanese Examined Patent Application, Second Publication No. H03-78325, it is described that engagement parts with which the positioning pins are engaged may be further provided in the storage portion.
A conveyance system including a positioning mechanism to position a handling mechanism (transfer device) with respect to a storage rack when transferring articles is also proposed (for example, see Japanese Unexamined Patent Application, First Publication No. H06-321316). The positioning mechanism described in Japanese Unexamined Patent Application, First Publication No. H06-321316, includes leg members disposed at the four corners of a frame of the handling mechanism so as to be capable of moving between a laterally-protruding state and a non-protruding state, and an operating device to operate the leg members. When the leg members are in the non-protruding state, the handling mechanism is permitted to go up and down. When the leg members are in the protruding state, the handling mechanism can be engaged with the storage racks in both sides. In addition, Japanese Unexamined Patent Application, First Publication No. H06-321316, discloses an embodiment in which each leg member includes a positioning surface having a triangular cross-sectional shape (V-shape) formed in a tapered shape, each storage rack includes a depressed part capable of being fitted to the positioning surface, and the positioning surface of the leg member is guided by the depressed part of the storage rack when positioning the handling mechanism.